✨potty training help✨

Help! My son turned three in October and has been “potty trained” for a year but we are still having issues with him pooping in his pants. Some weeks he tells us he has to poop and some days he doesn’t and will just go in his pants or hold it for a few days. I don’t know what to do. I’ve tried rewarding, potty charts, taking things away, just rolling with it, and nothing is working! Does anyone have any tips or has anyone else been through this?? He pees just fine but we are stugglinggggg with pooping 😩